The car has 260 000 miles. I changed the transmission fluid including the filter 3000 miles before. The fluid itself looks clean.

I disconnected the vacuum because two things happened with the vacuum connected:
1. it seemed to suck out the transmission fluid.
2. I couldn't switch to P or R anymore (I had to shut off the engine to do that). Without vacuum switching was no issue.
The vacuum that comes from the pump was adjusted and follows the correct curve about 8 inch in idle and 0 with full throttle.
My reasoning is that this is a modulator problem.
I could drive around without vacuum the past months without any trouble.

However now nothing works anymore unless I put full throttle then the gears engage very slowly.

The gears were always switching very soft - almost not noticeable (up / down). The gears were shifting too early. Only in the L position it switched correctly from 1st to 2nd gear. When I selected S it immediately switched to the 3rd gear. In D it switched to the 4th gear at relatively low RPM.

Now my car is sitting in my driveway ... today I changed the bushing of the linkage underneath... but no improvement...

I don't think a modulator change will improve anything at this point.
There must be something else.

Sebastian